The present invention relates generally to ultrasonic transducers, and more particularly to protective housings for such transducers.
Ultrasonic transducers operate to radiate ultrasonic waves through a medium such as air. In the environment of transducers, it is known that an ultrasonic transducer may be formed with either a linear or curved film incorporated therein.
Ultrasonic transducers are employed in various sensing devices such as distance meters, motion detectors or pen input devices. For example, an ultrasonic transducer mounted onto a movable pen or stylus radiates or receives ultrasonic signals through a medium (e.g. air) to a receiver system operative to calculate the position of the stylus. Letters or patterns formed from the movement of the stylus may be generated and stored in memory via a processor in a computer for display or for use in creating documents, files or graphics.
For many applications, it is desirable to provide a protective cover or housing for the transducer to minimize damage to the device through inadvertent contact, use, environmental conditions and the like. A problem with using conventional protective covers in front of a transducer, however, resides in their adverse impact on the transducer""s signal transmission output and/or sensitivity to received signals. A further problem is manifest in the prevailing view that protective covers or grids should have large openings to minimize such adverse impact on signal transmission characteristics. This results in structures that are far less rugged and more susceptible to damage due to inadvertent contact with a foreign object than desired.
A protective cover or grid for an ultrasound transducer comprises a series of vertically spaced members separated from one another by a pre-determined distance, each member being of substantially uniform width and arranged in a cylindrical shape. The protection grid includes a cavity for receiving a cylindrical transducer. The protection grid operates as both a physical protection mechanism for protecting the cylindrical transducer housed therein as well as operating as an impedance matching device.
In an alternative embodiment, a protection grid for housing an ultrasound transducer comprises a cylindrical tubing concentrically arranged with the transducer and having an opening at a first end for receiving the ultrasound transducer, the cylindrical tubing comprising a plurality of holes formed on the cylindrical surface thereof so as to provide a passageway for ultrasonic radiation. In a particular embodiment, the wall thickness may be about 1 millimeter and the inner diameter of the wall about 12.9 millimeters with the space between the transducer film surface and the inner surface of the wall being about 1.1 millimeters.
In combination with an omnidirectional ultrasound transducer comprising a cylindrical piezoresponsive material operative for transmitting and/or receiving ultrasound signals in a direction normal to the piezoresponsive material at a predetermined resonance frequency, a housing surrounding the ultrasound transducer for providing environmental protection and enhancing signal transmission. The housing comprises a base portion having an opening for receiving the ultrasound transducer and a cylindrical portion extending from the base portion for surrounding the ultrasound transducer cylindrical piezoresponsive material. The cylindrical portion comprises a plurality of slots disposed about the cylindrical portion for passing ultrasound radiation. The plurality of slots are arranged in a predetermined fashion and spaced apart from one another such that the total area of the plurality of slots is about 55% of the area of the cylindrical portion, whereby the cylindrical portion operates as an impedance matching layer with the ultrasound radiation for increasing the sensitivity or output transmission of the transducer.